This invention relates to a device for detecting the phase on an R.F. transmission line, which is useful for indicating the resonance condition of a complex load impedance (such as an antenna).
Various types of phase detectors, SWR indicators, forward and reflect power measuring devices, etc., have been known for many years. These devices are coupled into the transmission line, often between a transmitter and an antenna tuner. A Phase-Angle Detector for R.F. Transmission Lines is described in QST, July 1952, pages 17-20. However, that and most (if not all) other circuits to date use some form of wire-wound transformer to generate the vector voltages necessary for a phase indication, and that transformer can be the greatest source of problems in the design of a wide band instrument. Assymetry problems, spurious resonances, and non-linear response (due to the core material) are some of the most critical areas in transformer design.
Other prior art of interest includes the "Millimatch", a Matching Indicator for Low Power described in the A.R.R.L. Handbook, 1973 edition, pages 533-535, for giving a relative indication of forward and reflected power; U.S. Pat. No. 3,922,679 for a Wide Band Radio Frequency Phase Sensor; and my U.S. Pat. No. 4,071,819 for a Device for Sensing the Real Part in a Complex Impedance.